Hello.
This is my version, a stand along tiny utility for doing the task, save it as dusum.c in a directory, then type: make dusum, this works if you have Developer tools installed!
[code]#include <stdio.h>
int main( int argc, char **argv)
{
if (argc>1) {
fprintf(stderr,“dusum usage: du |dusum\n”) ;
return 1 ;
}
long double aLongDouble, theSum=0;
char digest[256];
while (!feof(stdin)) {
fscanf(stdin,“%Lf%s\n”,&aLongDouble,digest );
theSum+=aLongDouble ;
}
long double gigas = (long double)(theSum*512)/1000000000 ;
fprintf(stdout,“%.2Lf\n”,gigas);
return 0;
}[/code]
When dusum resides either in a path or with a path specified in front of it, you should be able to amened it at the end of the du statement, and get a result formatted as GB’s with two decimals back.
Edit
I couldn’t sleep as it nagged me that I may have had used a to small container for the number of blocks in a file, testing it originally in a folder where it was made. It is supposed to work properly now.
If not for anything else, this should serve as a demonstration of how quick it is to create a small c-program, once you have the tools installed.
C-programs like this are far faster to create if you know your way around with the scanf function (man -s3 scanf) and printf (man -s3 printf), than anything else. That it: when it comes to summing up stuff from standard input, where you would use bc or awk to perform the same. The important thing is to digest the line, so that you go on to the next one, which is the purpose of digest above: It reads the filename up to the newline, so that we go on to reading the number on the next line.
You gotta love Apple for making it so easy, when you have the tools installed! 
This way isn’t the most portable, but you may just fire up an editor, and make the executable, and later on, just drop it inside a script bundle and take it from there. And it is way faster to make the solution, than figure it out with bc, at least for me, I really deem this to be a to little job for awk, but it should be as fast to create as the C-version above:
#!/usr/bin/awk -f
{
a+=$1
}
END {
printf("%.2f\n",((a * 512 ) /1000000000))
}
You must make it executable with chmod +u dusum.awk, and either put it in a folder that is in your path, or specify the full path for it in the pipe where it comes right after the “du” statement.
